Method and apparatus for determining validity of mobile subscriber identifier in mobile communication terminal

ABSTRACT

A method and an apparatus for determining validity of a mobile subscriber identifier in a mobile communication terminal are provided. In the method, a temporary identifier assigned from a network is stored in a memory and a SIM card of the terminal. When a network authentication event occurs, the temporary identifier stored in the memory is compared with the temporary identifier stored in the SIM card. An identifier to be transmitted to the network is determined among an International Mobile Subscriber Identity (IMSI) and the temporary identifier stored in the SIM card depending on a result of the comparison.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed in the Korean Intellectual Property Office onJun. 30, 2008 and assigned Serial No. 10-2008-0062528, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus fordetermining the validity of a mobile subscriber identifier of a mobilecommunication terminal. More particularly, the present invention relatesto a method and an apparatus for determining the validity of a TemporaryMobile Subscriber Identity (TMSI) and a Packet Temporary MobileSubscriber Identity (PTMSI) recorded in a Subscriber IdentificationModule (SIM) card.

2. Description of the Related Art

Generally, in a mobile communication network which uses a Global Systemfor Mobile communication (GSM) and a Wideband Code Division MultipleAccess (WCDMA) system, a terminal may receive service from the networkafter passing through an authentication procedure. For example, whenpower is turned on, a terminal using a GSM scheme transmits userauthentication data stored in a SIM card to the network in order toperform the authentication procedure, and the network determines whetherthe terminal is eligible to receive service by checking the userauthentication data transmitted from the terminal. Examples of the userauthentication data stored in the SIM card include an InternationalMobile Subscriber Identity (IMSI), TMSI, and PTMSI. Here, the IMSI is aunique value corresponding to a subscriber that is assigned when asubscriber subscribes to a service. The IMSI does not change after beinginitially assigned, and includes a Mobile Country Code (MCC), a MobileNetwork Code (MNC), and a mobile subscriber identifier number. The TMSIand the PTMSI are temporary values identifying the terminal, arearbitrarily changed by the network, and may be used instead of the IMSIfor security purposes.

When a valid TMSI or PTMSI exists inside the SIM card, a conventionalterminal attempts to obtain a service from a network by preferentiallytransmitting the TMSI or PTMSI, rather than the IMSI, to the network.However, when a service is provided by authenticating a terminal usingonly the TMSI or PTMSI of the terminal, even users who have no authorityto use the service may still receive the service.

For example, to prevent some terminals from being used outside aspecific network, a mobile service provider provides a network lockfunction of checking an MCC and an MNC from the IMSI recorded in the SIMcard of the terminal, and, when an unauthorized MCC and MNC arereceived, preventing the terminal from performing a basic operation.However, in the conventional art, it has been reported that a terminalmay pass through such a network lock by replacing the MCC and MNC byspecific values, and then authenticate using a TMSI obtained from adifferent terminal during communication with the network, therebyobtaining a normal service for a relevant terminal.

Therefore, a technique of performing a network authentication procedurehaving higher security needs to be provided.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the abovementioned problems and/or disadvantages and to provide at least theadvantages described below. Accordingly, an aspect of the presentinvention is to provide a method and an apparatus for determiningvalidity of a mobile subscriber identifier in a mobile communicationterminal.

Another aspect of the present invention is to provide a method and anapparatus for determining validity of a Temporary Mobile SubscriberIdentity (TMSI) and a Packet Temporary Mobile Subscriber Identity(PTMSI) recorded in a Subscriber Identification Module (SIM) card of amobile communication terminal.

In accordance with an aspect of the present invention, a method fordetermining validity of a mobile subscriber identifier in a mobilecommunication terminal is provided. The method includes storing atemporary identifier assigned from a network in a memory and aSubscriber Identification Module (SIM) card of the terminal, when anetwork authentication event occurs, comparing the temporary identifiersstored in the memory with the temporary identifier stored in the SIMcard, and determining an identifier to be transmitted to the network,among an International Mobile Subscriber Identity (IMSI) and thetemporary identifier stored in the SIM card depending on a result of thecomparison.

In accordance with another aspect of the present invention, an apparatusfor determining validity of a mobile subscriber identifier in a mobilecommunication terminal is provided. The apparatus includes a memory forstoring a temporary identifier assigned from a network, a SIM card forstoring the temporary identifier assigned from the network and an IMSIassigned when a subscriber subscribes a service, and a controller forcomparing the temporary identifier stored in the memory with thetemporary identifier stored in the SIM card, and for determining anidentifier to be transmitted to the network depending on a result of thecomparison when a network authentication event occurs.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a block diagram illustrating a mobile terminal according to anexemplary embodiment of the present invention; and

FIG. 2 is a flowchart illustrating a procedure of determining validityof a mobile subscriber identifier in a mobile terminal according to anexemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention are provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

A technology for determining validity of a Temporary Mobile SubscriberIdentity (TMSI) and a Packet Temporary Mobile Subscriber Identity(PTMSI) recorded in a Subscriber Identification Module (SIM) card in amobile communication terminal according to an exemplary embodiment ofthe present invention is described below.

FIG. 1 is a block diagram illustrating a mobile terminal according to anexemplary embodiment of the present invention.

Referring to FIG. 1, the terminal includes a controller 100, a SIM card104, a storing unit 106, and a transceiver 110. The controller 100includes an identifier validity determination unit 102. The storing unit106 includes an identifier storing unit 108.

The controller 100 processes and controls operations of the mobilecommunication terminal, and more particularly, when a TMSI or PTMSI isreceived from a network through the transceiver 110, controls a functionfor storing the received TMSI or PTMSI in the SIM card 104 and thestoring unit 106. Also, when an event of having to transmit anInternational Mobile Subscriber Identity (IMSI), TMSI, or PTMSI to thenetwork occurs, the controller 100 determines whether there exists aTMSI or PTMSI having a valid value in the SIM card 104 using theidentifier validity determination unit 102, and determines whether theTMSI or PTMSI stored in the storing unit 106 and the TMSI or PTMSIstored in the SIM card 104 are the same through comparison. Also, thecontroller 100 determines which of the IMSI, TMSI, and PTMSI is to betransmitted to the network. When the stored TMSIs or PTMSIs are thesame, the identifier validity determination unit 102 determines totransmit the TMSI or PTMSI to the network. When the stored TMSIs orPTMSIs are not the same, the identifier validity determination unit 102determines that the SIM card 104 has changed, and determines to transmitan IMSI recorded in the currently inserted SIM card 104 to the network.Here, when the stored TMSIs or PTMSIs are not the same, the identifiervalidity determination unit 102 initializes the TMSI or PTMSI recordedin the SIM card 104 and then may transmit the initialized TMSI or PTMSIto the network. In an exemplary implementation, the identifier validitydetermination unit 102 initializes the TMSI or PTMSI recorded in the SIMcard 104 to a preset value. Also, when the TMSIs or PTMSIs stored in theidentifier storing unit 108 and the SIM card 104 are not the same, theidentifier validity determination unit 102 may control a series ofprocesses for being assigned a TMSI or PTMSI having a new value from thenetwork.

The SIM card 104 is attachable/detachable to/from the mobilecommunication terminal. The SIM card 104 may include a microprocessorand a memory chip and stores various information of a user. For example,the SIM card 104 may store an IMSI, TMSI, PTMSI and the like. Here, theTMSI is a value activated from a network for a voice call, and the PTMSIis a value activated from the network for a packet data service.

The storing unit 106 stores microcodes of a program for the process andcontrol of the controller 100, and various reference data. The storingunit 106 also stores temporary data generated during execution ofvarious programs, and various updatable data for storage. Moreparticularly, the storing unit 106 stores a TMSI or PTMSI provided bythe controller 100 in the identifier storing unit 108. Here, theidentifier storing unit 108 may include a nonvolatile memory wherestored data is retained even when the power of the terminal is turnedon/off.

The transceiver 110 converts a signal received from a base station viaan antenna to a baseband signal, provides the baseband signal to thecontroller 100, converts a signal provided by the controller 100 into anRF signal, and transmits the RF signal to the base station via theantenna. More particularly, according to an exemplary embodiment of thepresent invention, the transceiver 110 receives a TMSI or PTMSI from thebase station, provides the received TMSI or PTMSI to the controller 100,and transmits the IMSI, TMSI, or PTMSI provided by the controller 100 tothe base station.

FIG. 2 is a flowchart illustrating a procedure of determining validityof a mobile subscriber identifier in a mobile terminal according to anexemplary embodiment of the present invention.

Referring to FIG. 2, in step 201, the terminal determines whether a TMSIor PTMSI is assigned from a network via a base station. In an exemplaryimplementation, the TMSI or PTMSI may be assigned from a Home LocationRegister (HLR) of the network. Here, the TMSI or PTMSI may be assignedwhenever the terminal performs a location registration, or may beassigned while a service is performed after the location registration.That is, the TMSI or PTMSI may be arbitrarily reassigned from thenetwork.

When the TMSI or PTMSI is assigned, in step 203, the terminal stores theassigned TMSI or PTMSI in the identifier storing unit 108, which mayinclude a nonvolatile memory region of the terminal, and the SIM card104. In step 205, the terminal determines whether an event requiringnetwork authentication occurs. That is, the terminal determines whetheran event of having to transmit an IMSI, TMSI, or PTMSI to the networkoccurs. When the event does not occur, the terminal returns to step 201and repeats the subsequent steps.

On the other hand, when an event requiring network authenticationoccurs, the terminal determines whether there exists a TMSI or PTMSIhaving a valid value in the SIM card 104 in step 207. That is, theterminal determines whether a TMSI or PTMSI having a value within arange defined by specification is stored in the SIM card 104.

When there does not exist a TMSI or PTMSI having a valid value in theSIM card 104, the terminal performs an authentication procedure bytransmitting the IMSI stored in the SIM card 104 to the network in step221, and ends the operation according to an exemplary embodiment of thepresent invention.

On the other hand, when it is determined in step 207 that there doesexist a TMSI or PTMSI having a valid value in the SIM card 104, theterminal compares the TMSI or PTMSI stored in the identifier storingunit 108, which is the memory region of the terminal, with the TMSI orPTMSI stored in the SIM card in step 209. In step 211, the terminaldetermines whether the TMSI or PTMSI stored in the identifier storingunit 108 coincides with the TMSI or PTMSI stored in the SIM card 104.

When it is determined that the TMSI or PTMSI stored in the identifierstoring unit 108 coincides with the TMSI or PTMSI stored in the SIM card104 in step 211, the terminal performs the authentication procedure bytransmitting the TMSI or PTMSI of the SIM card 104 to the network instep 219, and ends the operation according to an exemplary embodiment ofthe present invention.

On the other hand, when it is determined that the TMSI or PTMSI storedin the identifier storing unit 108 does not coincide with the TMSI orPTMSI stored in the SIM card 104 in step 211, the terminal initializesthe TMSI or PTMSI of the SIM card 104 in step 213. In an exemplaryimplementation, the terminal may initialize the TMSI or PTMSI of the SIMcard 104 to a preset value.

In step 215, the terminal performs the authentication procedure bytransmitting the IMSI of the SIM card 104 to the network, ortransmitting the initialized TMSI or PTMSI to the network. Here, whenthe TMSI or PTMSI stored in the identifier storing unit 108 is differentfrom the TMSI or PTMSI stored in the SIM card 104, the terminal may beassigned a TMSI or PTMSI having a new value by performing a series ofprocesses with the network.

After that, the terminal ends the operation according to an exemplaryembodiment of the present invention.

According to an exemplary embodiment of the present invention, a mobileterminal stores a TMSI or PTMSI assigned from a network in a memory anda SIM card inside the terminal. When a network authentication procedureis required, the terminal compares the TMSI or PTMSI stored in thememory with the TMSI or PTMSI stored in the SIM card inside theterminal. When the TMSI or PTMSI stored in the memory coincides with theTMSI or PTMSI stored in the SIM card, the terminal transmits the TMSI orPTMSI to the network. When the TMSI or PTMSI stored in the memory doesnot coincide with the TMSI or PTMSI stored in the SIM card, the terminaltransmits the IMSI to the network. Therefore, when a SIM card isreplaced and inserted into the mobile terminal, security may be improvedby performing the authentication procedure on the basis of an IMSI ofthe replaced SIM card.

Although the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents. Therefore, thescope of the present invention should not be limited to theabove-described embodiments but should be determined by not only theappended claims but also the equivalents thereof.

What is claimed is:
 1. A method for determining validity of a mobilesubscriber identifier in a mobile communication terminal, the methodcomprising: storing, respectively, a first and a second temporaryidentifier assigned from a network in a memory and a SubscriberIdentification Module (SIM) card of the terminal; when a networkauthentication event occurs, comparing the first temporary identifierstored in the memory with the second temporary identifier stored in theSIM card and determining whether the second temporary identifier in theSIM card has a value within a valid range; when it is determined thatthe first and second temporary identifiers do not have a value withinthe valid range, performing an authentication with the network using anInternational Mobile Subscriber Identity (IMSI); initializing the secondtemporary identifier stored in the SIM card to a preset value when thefirst temporary identifier in the memory and the second temporaryidentifier in the SIM card, respectively, are not the same as a resultof the comparison; and determining to transmit the second initializedtemporary identifier to the network.
 2. The method of claim 1, whereinthe first and second temporary identifiers comprise at least one of aTemporary Mobile Subscriber Identity (TMSI) and a Packet TemporaryMobile Subscriber Identity (PTMSI).
 3. The method of claim 1, whereinthe memory comprises a nonvolatile memory.
 4. A mobile communicationterminal comprising: a memory for storing a temporary identifierassigned from a network; a Subscriber Identification Module (SIM) cardfor storing the temporary identifier assigned from the network, and anInternational Mobile Subscriber Identity (IMSI) assigned when asubscriber subscribes to a service; and a controller for comparing afirst temporary identifier stored in the memory with a second temporaryidentifier stored in the SIM card, for determining whether the secondtemporary identifier in the SIM card has a value within a valid range;and for determining an identifier to be transmitted to the networkdepending on a result of the comparison when a network authenticationevent occurs, wherein when the first temporary identifier in the memoryand the second temporary identifier in the SIM card, respectively, arenot the same as a result of the comparison, the controller determines toinitialize the second temporary identifier stored in the SIM card to apreset value, and transmit the initialized second temporary identifierto the network, and when it is determined that the first and secondtemporary identifiers do not have a value within the valid range,performing an authentication with the network using an InternationalMobile Subscriber Identity (IMSI).
 5. The method of claim 1, furthercomprising, when the first and second temporary identifiers stored inthe memory and the SIM card, respectively, are not the same as a resultof the comparison, being assigned a new temporary identifier from thenetwork.
 6. A mobile communication terminal comprising: a memory forstoring a temporary identifier assigned from a network; a SubscriberIdentification Module (SIM) card for storing the temporary identifierassigned from the network, and an International Mobile SubscriberIdentity (IMSI) assigned when a subscriber subscribes to a service; anda controller for comparing a first temporary identifier stored in thememory with a second temporary identifier stored in the SIM card, fordetermining whether the second temporary identifier in the SIM card hasa value within a valid range; and for determining an identifier to betransmitted to the network depending on a result of the comparison whena network authentication event occurs, wherein when the first temporaryidentifier in the memory and the second temporary identifier in the SIMcard, respectively, are not the same as a result of the comparison, thecontroller determines to initialize the second temporary identifierstored in the SIM card to a preset value, and transmit the initializedsecond temporary identifier to the network, and when it is determinedthat the first and second temporary identifiers do not have a valuewithin the valid range, performing an authentication with the networkusing an International Mobile Subscriber Identity (IMSI).
 7. The mobilecommunication terminal of claim 6, wherein the first and secondtemporary identifiers comprise at least one of a Temporary MobileSubscriber Identity (TMSI) and a Packet Temporary Mobile SubscriberIdentity (PTMSI).
 8. The mobile communication terminal of claim 6,wherein the memory comprises a nonvolatile memory.
 9. The mobilecommunication terminal of claim 6, wherein, when the first and secondtemporary identifiers stored in the memory and the SIM card,respectively, are the same as a result of the comparison, the controllerdetermines to transmit the second temporary identifier stored in the SIMcard to the network.
 10. The mobile communication terminal of claim 6,wherein when the first and second temporary identifiers stored in thememory and the SIM card, respectively, are not the same as a result ofthe comparison, the controller controls an operation for being assigneda new temporary identifier from the network.